I decided to take one of my goodnites( at random) ( new 2011 version) and pour water from measuring cups into the diaper.... I stopped at 9.25 cups, which equals 74 fluid OZ..... I estimate that .25 of 1 cup leaked out ( at various points, because I wasn't being careful enough with where I poured it. At 72- 74 oz,it became extremely full, stiff, and kinda difficult to put on. The outside of the diaper was totally dry, and I could have kept pouring more water ( maybe tomorrow Ill see what its absolute limit is - probably not more than 1 more cup)... I had to make room for my junk. I only wore it for about a minute because it was putting pressure on my testicles. Then I took it off and placed it on a plastic bag under my bed so that if osmosis occurs, my floor will not get wet.
I am going to do this with one of my older( last year's) goodnites for comparison.
Obviously, this is not a scientific test, because I'm not going to repeat it on my other 2011 goodnites ( maybe If I get another pack I will), so it is totally possible that this one had more SAP than the average goodnite. However, this diaper was randomly chosen for testing amongst a pack of 27,so there is no reason to suspect that the average diaper is Much better or worse in terms of Maximum absorbency.
In practice one will obviously not get this kind of performance because:
a.) after a few cups of urine, the diaper starts to sag and, for me at least, urine starts leaking out of the Back of the leg cuffs where a gap forms ( due to the diaper's wieght)
b.) if you go to fast, urine can over run the top of the leakgaurds and leak out of the diaper before it can be absorbed.
c.) Due to the natural landing spot from human anatomy, urine will not spread over the entire diaper.In particular, urine tends to land and pool between the legs, and towards the seat of the diaper. Even if it is contained initially, osmosis begins well before the 72+ OZ I reached during the experiment ( and when I stopped there still wasn't any osmosis).
d.) When wearing the diaper,one puts pressure on the sap, which over time, can force some of the liquid out. In addition, after a certain point,it becomes so swollen, that it doesn't fit well any more
e.) For men, the rate of urine as well as the max absorbency will depend on the position of the penis. For me, if it is placed so that urine can flow past the testicles, and to the back of the diaper, I can "flood" much more than if the testicles block the flowof urine forcing it up the diaper. In the latter case, urine flows up and over the leak gaurds before the diaper can absorb it.
I estimate that in practice, for me, the diaper has an effective capacity of 20 - 32+ Oz( then it usually starts leaking due to case a).
In the future,I'd like to buy my own set of measuring cups ( used my parents ofr this so only used water) and find out how many cups my average urination amounts too.